feat!: drop TagImplOptions in favor of Tag classes (#839)

Remove tag-options-adapter and the registerTag object-literal overload.
Custom tags must extend Tag.

Co-authored-by: Cursor <[email protected]>

test/stub/tags.ts

@@ -0,0 +1,32 @@
+import { throwIntendedError, rejectIntendedError } from './util'
+import { Tag } from '../../src/template/tag'
+import type { TagToken, TopLevelToken } from '../../src/tokens'
+import type { Liquid } from '../../src/liquid'
+
+export class ThrowingTag extends Tag {
+  render () {
+    throwIntendedError()
+  }
+}
+
+export class RejectingTag extends Tag {
+  async render () {
+    await rejectIntendedError()
+  }
+}
+
+export class ThrowsOnParseTag extends Tag {
+  constructor (token: TagToken, remainTokens: TopLevelToken[], liquid: Liquid) {
+    super(token, remainTokens, liquid)
+    throwIntendedError()
+  }
+  render () {
+    return ''
+  }
+}
+
+export class IntendedRenderErrorTag extends Tag {
+  render () {
+    throw new Error('intended render error')
+  }
+}